The 20-year-old rising star from Greece broke Andreozzi three times and held off a late comeback bid to reach the quarterfinals, where he will face Andreas Seppi of Italy. The eighth-seeded Seppi defeated Slovakian Martin Klizan 7-6 (2), 6-2.

Taylor Fritz, ranked No. 50 in the world, upset top-seeded fellow American John Isner 7-6 (3), 7-6 (5) on Wednesday to reach the quarterfinals in Auckland, New Zealand.

“John’s beaten me twice before,” Fritz said. “I really wanted to get the win on him. I knew I could. We had a lot of close points, and it just feels really good to get through that.”

By withstanding 26 aces and keeping his cool in the tiebreakers, the 21-year-old Fritz advanced to face British wild card Cameron Norrie. Norrie, who grew up in Auckland, had the crowd behind him during a 7-6 (5), 6-4 victory against Portugal’s Joao Sousa.

Other winners Wednesday included No. 2 seed Fabio Fognini of Italy, as well as No. 4 seed Pablo Carreno Busta of Spain, who advanced when countryman David Ferrer retired in the first set with a calf injury. Isner wasn’t the only top seed to fall, as American Tennys Sandgren cruised to a 6-3, 6-3 win against third-seeded Italian Marco Cecchinato.